Device for attaching and tensioning a sieve web



Feb. 20, 1968 A. ROHNER 3,369,662

DEVICE FOR ATTACHING AND TENSIONING A SIEVE WEB Filed Jan. 21, 1964 3 Sheets-Sheet 2 u INVENTOUR} E R THU R mwm 2% MW W United States Patent Ofifice Patented Feb. 20, 1968 3,369,662 DEVICE FOR ATTACHING AND TENSIONING A SIEVE WEB Arthur Rohner, Brussels, Belgium, assignor to Gebruder Buhler, Uzwil, Switzerland, a company of Switzerland Filed Jan. 21, 1964, Ser. No. 339,233 Claims priority, application Switzerland, Feb. 1, 1963, 1,268/ 63 15 Claims. (Cl. 209-403) This invention relates to sieves and, more particularly, to a novel and improved tensioning arrangement for tensioning a sieve web drawn over a sieve frame.

Sieves of the type to which the present invention is directed generally comprise an open frame having a sieve web stretched thereover and secured to the frame in the stretched or tensioned condition. It is desirable to be able to remove and replace the sieve web readily and easily, for various reasons well known to those skilled in the art. In interchanging or exchanging sieve webs, it is further desirable that tensioning means for the webs be readily releasable and that the tensioning means be so designed that it is easy to apply the proper tension to a replacement sieve web stretched over the sieve frame.

Accordingly, an object of the present invention is to provide an easily readjustable sieve tensioning means for stretching a sieve web over a sieve frame.

Another object of the invention is to provide such a tensioning device which is located as far as possible outside the flow path of material flowing through the sieve.

A further object of the invention is to provide a sieve, including a tensioning device, the sieve including a sieve frame having edges, a sieve web drawn over these edges and extending at an angle therefrom, sieve tensioning means connected with the sieve web, and cooperating sets of elements arranged, respectively, On the sieve tensioning means and on the sieve frame and having interengageable teeth, projections or noses, the elements of at least one set being provided with a plurality of teeth.

Still another object of the invention is to provide a sieve tensioning arrangement of the type mentioned in the preceding paragraph in which the noses are provided in the form of-barbed hooks. A further object of the invention is to provide a tensioning arrangement of the type mentioned for cooperation with a sieve frame formed by U-profiles or channels which are arranged to open outwardly of the frame, the tensioning means being located within these outwardly opening U-p-rofiles or channels.

Yet another object of the invention is to provide a tensioning devi ce including tensioning ledges and clamping ledges engaging the sieve web therebetween and interconnected by bayonet joint pins.

A further object of the invention is to provide a sieve including a frame and a sieve web tensioned over the frame, and having a pair of strips of cushioning material extending along the sieve web, stretched over the sieve frame, to act as sealing elements when two or more sieves are stacked one on the other.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a partial sectional view of a sieve, illustrating a first embodiment of a sieve tensioning device in accordance with the invention;

FIG. 2 is a view similar to FIG. 1 and illustrating a second embodiment of a sieve tensioning device in accordance with the invention;

FIG. 3 is a sectional view taken on the line III-III of FIG. 2, and illustrating a bayonet joint interconnecting a tensioning ledge and a clamping ledge;

FIG. 4 is a plan view, partly in section, taken along the lines IVIV of FIG. 2;

FIGS. 5, 7 and 8 are views, similar to FIGS. 1 and 2, showing further embodiments of the sieve tension device in accordance with the invention; and

FIG. 6 is a partial elevation view, partially in section, illustrating another embodiment of a sieve tension device in accordance with the invention.

Equivalent structural elements are denoted by equivalent reference characters in the various figures.

In each of the embodiments, the sieve frame proper is formed by U-profiles or channels 1 which open outwardly. The sieve illustrated in the drawings is intended, for example, for use in a plan sifter and is provided along its lower surface with sliding ledges 2, as best seen in FIG. 1.

Referring more particularly to FIG. 1, an angle profile 4, whose vertical leg is provided with teeth 6, is attached to the lower leg of a profile 1 by means of a screw or screws 3.

The sieve web 15 is clamped between a clamping ledge 10 and a tensioning ledge 11 by means of screws 12. The tensioning ledge 11 has a leg 16 which engages with the teeth 6 of the leg 5 of the angle profile 4.

In order to secure a safe engagement of the leg 16 with the teeth 6, the spring 17 biasing the tensioning ledge 11 is attached on the U-profile 1 by means of a rivet 18. The sieve formed by the U-profile 1, of which FIG. 1 shows part in sectional illustration, has for example a rectangular shape. On all sides of the rectangular sieve frame, i.e. on the U-profiles 1 forming the same, angular profiles 4 with teeth 6 are provided. Moreover, the sieve web is provided on all sides of the rectangle with tensioning ledges 11.

By this arrangement of the device with separate commercially available elements, a sieve tensioning device is formed which is readily tensionable and readjustable, and has the further advantage that it is arranged within the U-profiles or outwardly opening channels of the sieve frame, and accordingly has no elements projecting beyond the outer periphery of the frame, as defined by the outer edges of the channel legs, into the flow of the material run ning through the sieve and hampering such flow.

Neither are there elements projecting into the path for pulling the sieve apart. The exchanging of the sieve web can accordingly be carried out in a very short time with simple means.

FIGS. 2, 3 and 4 show a second embodiment of the sieve tensioning device. While in the device according to FIG. 1 a spring 17 is required for securing the meshing engagement of the leg 16 with the teeth 6, such a spring is dispensed within the device according to FIGS. 24.

The angle profile 4' is connected with the U-profile 1 of the sieve frame by the screws 3, with the formation of a partly closed box profile. The vertical leg 5' of the angle profile 4' has likewise teeth 6 which are undercut at 20.

The sieve web 15 is clamped between a tensioning ledge 22 and a clamping ledge 23 by means of bayonet bolts 24. The tooth 25 of the tensioning ledge 22 is provided with a nose 26. The nose 26 engages, as it were, like a barbed hook into the undercuts 20 of the teeth 6.

The bayonet bolts 24 are provided with transverse bars 28 and with a slotted head 29. Plate springs 30 are provided for producing a preloading. The pin 24 can be inserted into the clamping ledge 23 by means of a slot 31 provided therefor. An edge 32 of the clamping ledge 23 forms a fulcrum bearing on the tensioning ledge 22. By the pull of the bayonet bolt 24 applied to the clamping ledge 23, a clamping action is produced between the head 33 of the tensioning ledge 23 and the clamping ledge 22.

The longitudinal sides of the sieve lying opposite the sliding ledges 2 are provided each with a strip of two materials, which strip is stuck on andconsists of a lower foam material layer 36 and an upper felt layer 37. This strip 35 serves as a seal against a superimposed sieve or against a casing carrying the sieve.

As the sieve Web 15 is drawn over the outer corner 0f the U-profile 1 and the tooth 25 of the tensioning ledge 22 is provided with a nose 26 which, owing to the undercuts 20, can engage into the teeth 6, it is attained that a securing spring 17 is dispensed with. As the sieve web 15 is drawn readily into the U-profile 1, no unintentional disengaging of the tensioning ledge 22 can occur.

The construction of the clamping ledge 23 and the use of the bayonet bolt 24 allow a very rapid and simple exchange of the sieve web 15. As will be seen moreover from FIG. 4, merely some separate angle profiles 4' distributed over the length of the sieve edges, are required to have toothed legs 5' in order to attain a uniform tension of the sieve web over the entire area of the sieve. The adjustment of the tensioning ledge 22 for the purpose of tensioning the sieve relative to the appropriate teeth 6 of the angle profiles 4 can be carried out in a very simple manner, for example by means of a screw driver.

A third modified embodiment is illustrated in FIG. 5. Here the tensioning ledge 42 is provided with a tensioning grip 43. By means of screw 45 and clamping ledges 46, the sieve web 15 is clamped against the specially bent upper portion 47 of the tensioning ledge 42. A simply designed contact tooth 48 provided in the tensioning ledge 42 engages with the teeth 6. In order to secure a safe engagement of the tooth 48 in the teeth 6, a spring 50 is provided on the tensioning ledge 42 opposite U-profile 1 of the sieve frame.

This embodiment has the advantage, as compared with the embodiments described herein above, that, owing to the tensioning grip 43, the reloading of the sieve is simplified.

A fourth modified embodiment is illustrated in FIG. 6. U-profiles 1' likewise form the sieve frame. Near the corners of the sieve frame, angle pieces 51 are arranged, each having one leg 52 formed with teeth 53 pointing in the direction of the edge of the sieve frame. The angle pieces 51 are attached by means of screws 55 of the U- profiles 1' of the sieve frame. Bar shaped tensioning ledges 56 are provided at their ends with noses 57, which engage with the teeth 53. The sieve web 15 is retained between the tensioning ledges 56 and clamping ledges 58 by means of screws 59. For comparatively small sieves, this arrangement of the device may have the advantage that the general arrangement is simplified. In particular the accessibility for the engaging and disengaging of the tensioning ledges into the toothed legs 52 is simplified.

FIG. 7 shows a fifth modification similar to the third modification according to FIG. 5. Here the angle piece 4" with the leg 5 is provided merely with one nose 60, which engages with the teeth 61 of the tension ledge 42. A spring 50 secures a safe engagement of the teeth 61 and the nose 60.

A further modified embodiment is illustrated in FIG. 8. Here the angle piece 4 is attached, by means of screws 3 to the upper leg of the U-shaped profile 1 of the sieve frame in such a manner that the leg 5, with its teeth 6, extends downwardly. The sieve web 15 is drawn around the edge 70 of the leg 5 and is clamped between a tensioning ledge 71, with a nose 72, and a clamping ledge 73, with a notch 74.

Notch 74 serves for the insertion of a screwdriver or similar tool in order to force the tensioning ledge 71 upward and thereby to load the sieve web 15. By the manner teeth 6, a safe engagement of the meshing elements is atledge '71 and accordingly to the nose 72 relative to the of applying the pull of the sieve web 15 to the tensioning tained.

The device has primarily the advantage that any dust particles cannot be deposited in difliculty accessible corners, but can accumulate only in the lower corner of the U-shaped profile 1, which can be readily cleaned.

Although the various modified embodiments of the sieve tensioning device have been described in principle for rectangular sieve frames, the possibility of using the invention for circular or otherwise shaped sieves is not excluded. Without departing from the idea of the invention the use of other structural elements of machine construction is possible without difliculty. The essential feature of the device according to the invention consists in that the sieve web is drawn over an edge, preferably the outer edge of the sieve, downwardly, and that, for tensioning two intermeshing toothed racks are used, one of which is connected with the sieve frame and the other with the sieve web. Moreover a U-shaped sieve frame should not be a restricted feature. On the contrary, the latter my be formed from other known structural elements.

While I have herein described and illustrated in the accompanying drawings what may be considered typical and particularly useful embodimentts of my said invention, I wish it to be understood that I do not limit myself to the particular details and dimensions described and illustrated.

What I claim as my invention and desire to secure by Letters Patent is:

1. A sieve with a sieve tensioning device, comprising, in combination, an open sieve frame formed of outwardly opening structural members having at least a generally horizontal upper leg and a generally vertical leg; a sieve web having its entire periphery drawn over the edges of the upper legs and extending downwardly and inwardly at an angle; first tensioning elements each secured within a structural member and extending substantially parallel to said vertical leg thereof towards the upper leg thereof but terminating in spaced relation to the latter; and second tensioning elements secured along the edges of said web and positioned within said structural members, each second tensioning element including an elongated ledge member and an elongated clamping member clamping the edge of the web therebetween, and fastening means securing each clamping member to the associated ledge member; one of each of said first and second tensioning elements being formed with multitoothed racks which, at least in the tensioned condition of said sieve web, extend substantially parallel to said vertical legs and in spaced relation thereto; each of the other of said first and second tensioning elements having at least one tooth engageable with the teeth of an associated rack to tension said sieve web; all of said teeth being interengaged within the frame outer periphery defined by the outer edges of said upper legs, and being engaged Within said structural members.

2. A sieve as claimed in claim '1, comprising barbed hooks provided on said teeth.

3. A sieve, as claimed in claim 1, in which the teeth of said racks extend downwardly and inwardly toward the inner surfaces of the associated one channel legs.

4. A sieve as claimed in claim 3, wherein said first tensioning elements are mounted on the legs of said channel members which are spaced from the legs over which said web is drawn.

5. A sieve as claimed in claim 3, wherein said first tensioning elements are mounted on the legs of said channel members over which said web is drawn.

6. A sieve, as claimed in claim 1, wherein said sieve frame is angular in plan and said tensioning elements are arranged near the corners of said sieve frame.

7. A sieve as claimed in claim 6, wherein the teeth of said first tensioning elements are arranged parallel to the edges of said sieve frame.

8. A sieve as claimed in claim 6, wherein the teeth of said first tensioning elements are arranged in the direction of the edges of said sieve frame.

9. A sieve, as claimed in claim 1, including springs biasing the teeth of said tensioning elements into engagement with each other.

10. A sieve as claimed in claim 9, wherein said springs are arranged between said ledge members and said sieve frame.

1-1. A sieve, as claimed in claim 1, wherein tensioning grips on said ledge members to facilitate manipulation of the latter.

'12. A sieve, as claimed in claim 1, including laminated cushioning strips extending in parallel spaced relation across said sieve web and each including a layer of foam material in engagement with said sieve web and a layer of felt on the outer side of said layer of foam material; said str-ips forming seals when another sieve is superposed on said first-mentioned sieve or when said sieve is placed in a casing.

13. A sieve with sieve tensioning device, comprising in combination, a sieve frame having peripheral edges, a sieve web having its entire periphery drawn over the edges of said sieve frame, sieve tensioning elements connected with said sieve web around the periphery thereof, a first set of toothed elements arranged on said sieve frame and a second set of toothed elements included in said tensioning elements and engaging with the toothed elements of said first set, the toothed elements of at least one of said sets being constructed as toothed racks having a plurality of teeth for regulating the tension of said sieve web by engaging teeth of the toothed elements of the other set with selected teeth of said tooth racks, each of said tension-ing elements including a tensioning ledge member and a clamping ledge clam-ping said sieve web against said ledge member, and joint means interconnecting each clamping ledge and the associated ledge member.

14. A sieve as claimed in claim 13, wherein said clam-ping ledges are supported at least partly pivotally relative to said ledge members.

15. A sieve with sieve tensioning device, as claimed in claim 13, in which said joint means comprises bayonet joint pins.

References Cited UNITED STATES PATENTS 2,114,406 4/ 1938 Simpson 209403 2,310,236 2/ 1943 Hauge 209-403 X 3,176,843 4/ 1965 Hoskins et al. 20940 3 1,960,095 5/ :1934 Tonnesen 160-327 3,126,332 3/ 1964 Salete 209-408 FRANK W. LUT IER, Primary Examiner.

HARRY B. THORNTON, Examiner.

L. H. EATHERTON, Assistant Examiner. 

1. A SIEVE WITH A SIEVE TENSIONING DEVICE, COMPRISING, IN COMBINATION, AN OPEN SIEVE FRAME FORMED OF OUTWARDLY OPENING STRUCTURAL MEMBERS HAVING AT LEAST A GENERALLY HORIZONTAL UPPER LEG AND A GENERALLY VERTICAL LEG; A SIEVE WEB HAVING ITS ENTIRE PERIPHERY DRAWN OVER THE EDGES OF THE UPPER LEGS AND EXTENDING DOWNWARDLY AND INWARDLY AT AN ANGLE; FIRST TENSIONING ELEMENTS EACH SECURED WITHIN A STRUCTURAL MEMBER AND EXTENDING SUBSTANTIALLY PARALLEL TO SAID VERTICAL LEG THEREOF TOWARDS THE UPPER LEG THEREOF BUT TERMINATING IN SPACED RELATION TO THE LATTER; AND SECOND TENSIONING ELEMENTS SECURED ALONG THE EDGES OF SAID WEB AND POSITIONED WITHIN SAID STRUCTURAL MEMBERS, EACH SECOND TENSIONING ELEMENT INCLUDING AN ELONGATED LEDGE MEMBER AND AN ELONGATED CLAMPING MEMBER CLAMPING THE EDGE OF THE WEB THEREBETWEEN, AND FASTENING MEANS SECURING EACH CLAMPING MEMBER TO THE ASSOCIATED LEDGE MEMBER; ONE OF EACH OF SAID FIRST AND SECOND TENSIONING ELEMENTS BEING FORMED WITH MULTITOOTHED RACKS WHICH, AT LEAST IN THE TENSIONED CONDITION OF SAID SIEVE WEB, EXTEND SUBSTANTIALLY PARALLEL TO SAID VERTICAL LEGS AND IN SPACED RELATION THERETO; EACH OF THE OTHER OF SAID FIRST AND SECOND TENSIONING ELEMENT HAVING AT LEAST ONE TOOTH ENGAGEABLE WITH THE TEETH BEING INTERENGAGED WITHIN SAID SIEVE WEB; ALL OF SAID TEETH BEING INTERENGAGED WITHIN THE FRAME OUTER PERIPHERY DEFINED BY THE OUTER EDGES OF SAID UPPER LEGS, AND BEING ENGAGED WITHIN SAID STRUCTURAL MEMBERS. 